A number of devices monitor the presence of organic compounds in aqueous streams. Potential uses for such devices include the monitoring of aqueous streams in chemical plants, water purification plants, power plants, food processing plants, semiconductor plants, pharmaceutical plants and the like.
In one approach, disclosed in Regan, U.S. Pat. No. 3,958,941, an aqueous sample is periodically injected into a line which feeds into a reactor in which it is exposed to ultraviolet irradiation which oxidizes the organic carbon content to CO.sub.2 gas. The generated CO.sub.2 is mixed with water in a resistivity (or conductivity) cell which is stated to measure the amount of initially present organic carbon as a decrease in resistance in water present in the resistivity cell. Air strips off water insoluble gases and bubbles through deionized water held separately in the resistivity cell. The gases are reabsorbed therein, and the conductivity is measured as an indication of gases is ionized in the water. Possible gases include CO.sub.2 and H.sub.2 S. This system is primarily useful for analysis of high purity water and is based on the complete oxidation of organics to carbon dioxide. It is a complicated and expensive system to build and its batch-type sample addition limits the time when samples may be detected and requires the presence of a technician to periodically inject sample. Also, it requires complete oxidation to CO.sub.2 which is difficult and time consuming.
Another batch-type ultraviolet system is sold by Anatel Instrument Corporation of Boulder, Colo., under the designation A-100 TOC. It suffers from the deficiencies of batch operation discussed above. Also, it is subject to malfunction due to valve opening and closing operations for each cycle. Furthermore, it is relatively expensive because it requires sophisticated electronics to measure rate changes during the oxidation cycle.